Temperature monitoring device containing at least one element of an alloy which memorizes its shape

ABSTRACT

This device comprises a casing (2) of synthetic material containing a motor element (7) made of at least one alloy which memorizes its shape and having associated with it a movement transmission element consisting of a piston (9) and a rod (10) and acting on at least one indicator element (4) irreversibly recording each overstepping of a predetermined temperature, the casing being provided with transparent windows permitting the state of the indicator element or elements to be viewed. 
     Application to the monitoring of the overstepping of a temperature.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a division of Ser. No. 07/619,193 filed Nov. 27,1990 (U.S. Pat. No. 5,143,453)as a division of Ser. No. 07/499,333 filedJun. 1, 1990 (U.S. Pat. No. 5,018,874) as a national phase ofPCT/FR89/00510 filed Oct. 3, 1989 and based, in turn, upon Frenchnational application 88 13245 of Oct. 4, 1988 under the InternationalConvention.

FIELD OF THE INVENTION

The present invention relates to a temperature monitoring devicecontaining at least one element of an alloy which memorizes its shape(i.e. a shape-memory element).

BACKGROUND OF THE INVENTION

In numerous fields it is necessary to record the temperature variationsto which a product is subjected, in cases where, depending oncircumstances, one or more variations or the overstepping ofpredetermined temperatures could make the product unsuitable forsubsequent use.

One common example relates to the field of foodstuffs, where it isnecessary to check continuously the quality of the refrigeration ofperishable produce: fresh, deep-frozen and frozen products, or foodswhich must be kept at a certain temperature.

It is however not exceptional for such products, in the course of thevarious manipulations to which they are subjected, to exceed apredetermined temperature above which they may be damaged.

It is also important to check continuously the quality of the coldsupplied by equipment producing or maintaining cold, such asrefrigerators or freezers, since an operating fault may result in a risein temperature injurious to the products contained in them.

It is also necessary to maintain a continuous quality check onsterilization processes, in respect of both the products sterilized andthe sterilization equipment.

Where health is concerned, it is necessary to maintain a continuouscheck on the conditions of conservation of blood or products derivedfrom blood, biological and biogenetic products or certain pharmaceuticalproducts for which temperatures must be strictly respected.

In the medical field, it is also necessary to maintain a continuouscheck on transplant organs and animal and human gametes.

In the industrial field, it is also desirable to monitor the operatingtemperature of certain machine parts, the manufacturing temperature ofcertain components, particularly electronic components, and also thestorage temperature of various materials, such as composite materials orphotographic emulsions, for example.

In addition, in the industrial field, temperature variations are incertain cases accompanied by variations of pressure which it isnecessary to check continuously. These include for example, variationsin pressure pipes monitored with the aid of instrumented valves.

It is therefore important to have available a simple, reliable devicecapable of being attached to the product and/or machines and ofindicating by direct reading the overstepping of a determinedtemperature.

French Patent No. 2 560 992 in the name of the Applicant relates to adevice in which the overstepping of a determined temperature isindicated by an irreversible coloration triggered with the aid of anelement made of an alloy which memorizes its shape.

OBJECTS OF THE INVENTION

An object of the present invention is therefore to provide a device,made of an alloy which memorizes its shape, which enables temperaturesto be monitored. Other objections relate to a device which

is capable of detecting a plurality of oversteppings of the temperature,while storing the number of oversteppings;

is capable of having a variable response time ("delay time") on each ofthe temperature thresholds, which is at present not the case for alldevices, including that of French Patent No. 2 560 992;

includes a tamperproof system for the display of each of the temperaturethresholds;

operates in all positions;

is resistant to shocks, vibrations, radiation and corrosion;

can be produced and stored at ambient temperature whatever theutilization temperatures; and

is self-activating on passing through the different temperaturethresholds.

To this end, the device to which the invention relates comprises acasing of synthetic material containing a motor element made of at leastone alloy which memorizes its shape and having associated with it amovement transmission element consisting of a piston and a rod andacting on at least one indicator element irreversibly recording theoverstepping of a predetermined temperature, said casing being providedwith transparent windows enabling the state of the indicator element orelements to be viewed.

The motor element makes use of a material of an alloy of known type,which memorizes its shape, for example of the copper-nickel-aluminum,copper-zinc-aluminum or titanium-nickel type, or else it may be made ofother ternary or quaternary alloys.

BRIEF DESCRIPTION OF THE DRAWING

The invention will be described in greater detail with reference to theaccompanying schematic drawings showing, as nonlimitative examples, anumber of embodiments of this device, which is intended for monitoringthe crossing of temperature thresholds. In the drawing

FIGS. 1 to 3 are three views in longitudinal section of a first devicein the course of three operating phases;

FIGS. 4 to 6 are three views in longitudinal section of a second devicein the course of three operating phases;

FIGS. 7 to 9 are three sectional views of a third pivoting device in thecourse of three operating phases;

FIGS. 10 to 12 are three views in longitudinal section of a first lineardisplacement device in the course of three operating phases;

FIGS. 13 to 15 are three views in longitudinal section of a secondlinear displacement device in the course of three operating phases;

FIGS. 16 and 17 are two views in longitudinal section of a variant ofthe device shown in FIGS. 13 to 15;

FIG. 18 is a view of the outside of the casing of a device correspondingto one of the embodiments of FIGS. 13 to 17;

FIG. 19 shows a second constructional variant of the device of FIGS. 13to 15;

FIGS. 20 to 23 show a constructional variant of the device of FIG. 19,with the introduction of elements increasing thermal inertia;

FIGS. 24 to 26 are three views in section of another device;

FIGS. 27 to 30 are four views in section of a first variant of thedevice shown in FIGS. 24 to 26;

FIGS. 31 to 34 are four views in section of a second variant of thedevice shown in FIGS. 24 to 26;

FIGS. 35 to 37 show three views in section of a device enabling thedurations of the overstepping of the various predetermined temperaturethresholds to be indicated; and

FIG. 38 shows a rotary actuator which memorizes its shape.

SPECIFIC DESCRIPTION

The device shown in FIGS. 1 to 3 comprises a casing 2 ofparallelepipedic general shape, in which a wheel 4, on the periphery ofwhich teeth 5 are regularly spaced, is mounted for rotating about anaxis 3.

As can be seen from the drawing, the teeth 5 are directed towards thereal in relation to the direction of rotation of the wheel. The wheelcan turn in one direction only since a resilient tongue 6 forming anonreturn pawl is supported in each stable angular position of the wheelin the bottom of the cavity formed at the rear of a tooth 5, thuspreventing the rotation of the wheel in the clockwise direction.

A spring 7 of an alloy which memorizes its shape (i.e. shape-memoryalloy, is mounted in a cylinder 8 whose axis is substantially tangentialto the circumference of the wheel, one end of said spring being fixedagainst the bottom of the casing while its other end is fixed on apiston 9 mounted for sliding in the cylinder 8, from the other face ofwhich piston a rod 10 projects, the free end of which is equipped with ametal blade 12 prestressed in the direction of the wheel axis 3 andintended to come to be supported in the cavity disposed at the rear of atooth 5 on the wheel 4.

As shown in FIGS. 1 to 3, the wheel 4 is provided, facing each tooth 5,with a mark 13, which in the present case is in the form of a numeral.Each mark 13 is visible through a transparent window 14 when it issituated facing the window. Finally, the wheel 4 has a finger 15projecting laterally and intended to come to bear against a stop 16fastened to the casing when the wheel has pivoted less than one turn, inorder to prevent the same marks 13 from coming in succession more thanonce to face the window 14. It should be noted that the distance betweentwo adjacent teeth 5 on the wheel corresponds to the stroke of thespring 7 in the course of a deformation of the latter.

The device functions is as follows:

At ambient temperature the spring 7 is elongated as shown in FIG. 1, thepiston 9 being situated in the top position and the metal blade 12 beinginserted into the cavity situated at the rear of the tooth bearing thereference (2). The window 14, and also a window 17 situated on the pathof travel of the spring, allow no particular distinctive sign to beseen.

When the temperature of the casing has been lowered to the storagetemperature of the product to be monitored, the spring 7 contracts untilits turns are substantially contiguous, carrying with it in its strokethe piston 9, which takes up position facing the window 17, and themetal blade 12, the end of which comes to lie in the cavity situated tothe rear of the tooth bearing the reference (3).

The fact that the user can view the piston 9 through the window makes itpossible to know that the product and the device associated with it areactually at the selected preservation temperature.

If the temperature rises above a predetermined threshold, the spring 7resumes its elongated configuration, as shown in FIG. 3, the metal blade12, in the course of the relaxation of the spring, driving the wheel 4to rotate in the counterclockwise direction, the end of the rotationbeing such that the window 14 makes it possible to view the toothbearing the reference (1). At the same time the piston 9 disappears fromthe window 17, which indicates that the normal storage temperature hasbeen overstepped and that this rise in temperature is still continuing,because the piston is not visible in the window 17.

When the temperature falls again, the spring contracts and the piston 9is once again visible through the window, indicating that the storagetemperature has been reached again, although the information supplied inthe window 14 indicates that the product has overstepped the normaltemperature threshold. It is thus possible to see immediately the numberof oversteppings of the temperature, this number being able to be atmost equal to the number of teeth on the wheel, since the latter isnecessarily prevented from rotating when the finger 15 bears against thestop 16; a plurality of successive rotations of the wheel cannot in factmake it possible to record an exact number of oversteppings of thetemperature.

It is possible to use in association a plurality of wheels of differentdiameters (see FIG. 3), which are operated in succession when the wheelof larger size has made one turn; a larger number of oversteppings ofthe temperature can thus be detected.

FIGS. 4 to 6 show a device similar to the preceding device, that is tosay one having a notched wheel, the same elements therein being giventhe same references numerals as previously.

In this device the toothed wheel 4 is equipped, in a plane parallel tothat containing the teeth, with an equal number of buckets 18 arrangedin the same angular distribution and leading out to the outside. Amagazine 19 containing balls 20 is mounted adjacent to the cylinder 8containing the spring 7 of an alloy which memorizes its shape, therespective axes of the cylinder 8 and magazine 20 being at right anglesto one another. The opening of the magazine 19 can be closed by a slide22 adapted to be moved by the rod 10 associated with the piston 9. Thesize of the buckets 18 is such that each of them can receive a ball 20,each ball being retained in the bucket receiving it by means ofresilient tongues 23 disposed at the edge of the bucket.

This device functions in the following manner:

At ambient temperature, and as shown in FIG. 4, the balls 20 are lockedin the magazine 19 by the slide 22. When the temperature falls to thestorage value, the spring 7 is compressed, carrying with it in itsstroke the rod 10 and the slide 22, which opens the magazine 19. Thefirst ball, which may for example be a ball which is green in color, ispushed by the following balls, which are subjected to the action of aspring 24, into the first bucket 18. If the temperature rises above apredetermined threshold, the spring resumes its elongated shape androtates the wheel 4 with the aid of the rod 10 and the metal blade 12,the slide 22 not being moved.

In the course of this rotation, a new bucket 18 comes to face themagazine 19, enabling a ball 20, which may be a red ball indicatingoverstepping of the threshold temperature to be received. A furtherlowering of the temperature enables the spring to be recompressed. Thetransparency of the top part of the casing, or at least of the zone ofit which is facing the path of travel of the bucket, makes it possibleto view immediately the number of oversteppings of the thresholdtemperature.

FIGS. 7 to 9 illustrate another device similar to the preceding devices,that is to say provided with a notched wheel adapted to be drivenrotationally every time the temperature is overstepped, wherein the sameelements are given the same references as previously. In this case thenotched wheel is associated with buckets 25, each of which is situatedfacing a tooth 5 on the wheel, each of these buckets having a closureflap 26.

In this embodiment a reservoir 27 containing a fluent medium, such aspowder, sand or a viscous liquid, is mounted adjacent to the cylinder 8containing the spring 7. The fluid is able to flow out of the reservoirby way of an opening 28 through the action of the pressure exerted by apiston 29 and a spring 30. A slide 32, which also has an opening 33, isfastened to the rod 10, the opening 33 being so positioned that it issituated opposite the opening 32 of the reservoir when the spring 7 isin the relaxed position.

At ambient temperature, illustrated in FIG. 7, as the openings 32 and 33lie opposite one another the first bucket 25 is filled with fluid. Whenthe temperature of the device is lowered below a predetermined value,the spring 7 is compressed and the slide 32 then closes the reservoir27, as shown in FIG. 8. When the threshold temperature is overstepped,the spring 7 is relaxed, thereby bringing about on the one hand therotation of the wheel 4 and the bringing of another bucket to face theopening 32 of the reservoir, and on the other hand the establishment ofcommunication between said opening 32 and the opening 33 in the slide.This bucket is filled until the temperature falls again, the amount ofthe flowable medium contained in the bucket making it possible not onlyto determine that the temperature had been overstepped, but also toestimate the duration of this overstepping, if the rate of flow of fluidout of the reservoir is known.

It is possible to provide a more elaborate apparatus comprising a secondmotor, of an alloy which memorizes its shape, to close the slide or theflaps as soon as the threshold temperature is passed in the oppositedirection, in such a Banner as to indicate the threshold oversteppingtime.

The device illustrated in FIGS. 10 to 12 is a linearly functioningdevice comprising an elongate body 34, for example of cylindrical shape.At one end of the casing 34 is mounted, inside the latter, a spring 35of a shape memory alloy which memorizes its shape, one end of which isfixed against the bottom of the casing, while its other end is fixed ona piston 36 fastened to a rod 37 extending in the lengthwise directionof the casing. On this rod 37 is mounted a cursor 38 provided with acentral opening and having a profiled body, that is to say having a sidewall diverging from the rod towards the outside and from the oppositeend of the casing to that which is equipped with the spring towards theend equipped with the spring. The rod is equipped with cogs 39 profiledoppositely to the cursor, in order to permit displacement of the rod, inrelation to the cursor, only in the direction of the spring 35. Thecasing is in turn provided on its inside face with cogs 40 which consistof a succession of inclined surfaces and surfaces at right angles to therod 37, permitting the displacement of the cursor only from the end ofthe casing provided with the spring towards its opposite end. The rod 37also carries, near the piston 36, a shoulder 42 intended to cooperatewith a ring 43 mounted loose on the rod between the piston 36 and saidshoulder. Close to its end situated near the piston 36 the casing 34 isprovided with a recess 44 disposed facing a window (not shown in thedrawing). It is to be noted that the stroke of the spring 35 in thecourse of a cycle of deformation corresponds substantially to the pitchof the cogs 40 on the casing.

The functioning of this device is as follows:

At ambient temperature, and before its first use, the device is in thestate illustrated in FIG. 10. When the temperature is lowered to thestorage value, the spring 35 is compressed, carrying with it in itsstroke the piston 36, the rod 37 and the shoulder 42. The latter causesthe ring 43 to pass into the recess 44, thus making it possible to viewinstantaneously the fall to storage temperature. It is to be noted thatin the course of this stroke, and as illustrated in FIG. 11, the cursor38 has not moved because It has remained locked by the cog 40, againstwhich it was bearing, while permitting the passage through its centralopening of a nonreturn cog 39 on the rod 37.

If the temperature rises above the threshold value, the spring 35 isrelaxed, thus bringing about the movement of the piston 36 and rod 37 tothe right. A cog 39 bearing against the cursor 38 moves the lattertowards the right in order to bring it into a locked position in thenext nonreturn cog 40. It is thus possible to view immediately thenumber of oversteppings of the threshold temperature, by counting thenumber of cogs 40 over which the cursor 38 has traveled. This is madepossible by the provision of a window in the body of the casing, on thepath of travel of the cursor 38, and the Barking of graduations alongthis window.

FIGS. 13 to 15 illustrate a constructional variant of the device inFIGS. 10 to 12, the same elements being given therein the samereferences as previously.

In this case the spring 35, made of an alloy which memorizes its shape,is fixed, not against the bottom of the casing, but against the bottomof a second cursor 45 fulfilling the function of the piston 36previously described, the spring 35 bearing directly against the cursor38. The rod 37 fastened to the cursor 45 passes through said cursor 38and its free end carries a shoulder 46 serving as support for abalancing spring 47, the other end of which bears against the cursor 38.When the device is at ambient temperature, as shown in FIG. 13, thespring 35 is relaxed and the two cursors 38 and 45 are separated bythree cogs 40 on the casing 34. When the temperature of the device fallsand when the storage temperature is reached, the spring is compressed.With the cursor 38 locked against a cog 40, the cursor 45 accompaniesthe spring in its movement, so that at the end of the compression thetwo cursors are situated against neighboring cogs, as shown in FIG. 14.A window, not shown in the drawing, makes it possible to view theposition of the two cursors. If when the temperature rises the thresholdtemperature is reached and then overstepped, the spring 35 islengthened, and since the cursor 45 is locked against the cog 40 withwhich it is in contact, only the cursor 38 can accompany the movement ofthe spring and be displaced by one cog. If the temperature continues torise, the cursor 38 can continue to be displaced because of thecorresponding elongation of the spring 35.

The presence of the balancing spring 47 makes it possible to avoidfastening together the end of the spring 35 and the cursor 38 and tocompensate for hysteresis phenomena connected with the functioning of aspring of an alloy which memorizes its shape.

If the spring 35 is fixed at both ends, on the cursor 38 and on thecursor 45 respectively, and if there are no hysteresis phenomena, It ispossible to dispense with the balancing spring 47.

The device is then in the simplified form shown in FIGS. 16 and 17,which respectively show the spring in the relaxed position and in thecompressed position.

FIG. 18 illustrates very schematically the outside of a casing, and moreparticularly the series of windows provided in the latter. These windows48 and 49, are grouped in pairs, with the exception of the window 41 onthe extreme right at which the cursor 45 is situated and whichcorresponds to the normal manufacturing temperature (ambienttemperature). At the manufacturing temperature the cursor 45 is in thewindow 41, while the cursor 38 is in the window 49. At normal storagetemperature (low temperature ) the cursor 45 has passed into the window48, while the cursor 38 has passed into the window 49. After thetemperature has for the first time overstepped the storage temperature,the cursor 45 has passed into the window 48, while the cursor 38 hasremained in the window 49₁. When the low storage temperature is reachedonce again, the cursor 45 passes into the window 48₁.

The indices_(i) of the windows 48_(i) and 49_(i) thus indicate thenumber of oversteppings of the storage temperature and,depending on theposition of the cursor 45, the return or failure to return to thestorage temperature after the overstepping.

Depending on the thickness of the casing 34, there will be a longer orshorter delay time on the overstepping of temperatures, varying from afew minutes to several hours according to the desires of the user whenthe device is manufactured.

It is possible to modify the casing in respect of the position of thewindows 49_(i) relative to 48_(i) and to follow the pair 45-46 (insteadof 45-38 ) in its respective movements.

It is interesting to provide cursors of different colors: 45 being greenand that or those designated 38 (and 46) being red, for example. Theuser will thus be able to deduce immediately the number of oversteppingsof the normal storage temperature.

FIG. 19 illustrates a constructional variant of the preceding devices,wherein the two cursors 38 and 45 are no longer connected to one anotherby a rod sliding through the cursor 38, but only by the spring 35 of analloy which memorizes its shape. It is to be noted that the cursor 38may itself be of an alloy which memorizes its shape, in order tointervene in respect of the conditions under which it is moved andlocked in the cogs 40 in dependence on the storage and thresholdtemperatures.

FIGS. 20 to 23 illustrate a variant of the device shown in FIGS. 16, 17and 19, wherein means are provided which enable the deformation of theelement 35 of an alloy which memorizes its shape to be delayed on theoverstepping of a threshold temperature. For this purpose, the casing isprovided on its periphery with a certain number of elements 50 offsetaxially relative to each other, each of them extending over a lengthcorresponding to three cogs, while their upstream portion 52 (referringto the direction of movement of the spring 35) is smaller than thethickness of the downstream portion 53.

At ambient temperature the spring 35 is in its elongated position andthe two cursors 38 and 45 are separated by three cogs. In conjunctionwith the body of the casing they delimit a chamber 54. The slightthickness of the body of the casing permits rapid thermal diffusion, sothat, when the temperature falls to the set point, the spring 35contracts very rapidly until the cursor 45 comes to bear against a cogadjacent to that against which the cursor 38 is bearing. In thisposition the volume delimited between the two cursors is situated, asshown in FIG. 21, facing the portion 52 of slight thickness of the firstelement 50. When the temperature oversteps the threshold temperature,the element 50, because of its thermal inertia, retards the responsetime of the spring. When the spring is relaxed, the cursor 38 moves atthe same time as the spring, as shown in Figures 22 and 23.

By making use of the thickness of material of the elements 50 it ispossible to adjust the response time of the spring 35, and optionally tohave available a plurality of elements of different thicknesses in orderto introduce specific inertias for the different oversteppings.

FIGS. 24 to 26 illustrate another device comprising a casing 55 ofparallelepipedic general shape, in which are provided two elongatechambers disposed at right angles to one another and leading one intothe other. The first chamber 56 contains at one end a spring 57 of analloy which memorizes its shape and being fastened at one end to thebottom of the chamber, while one end bears against a piston 58 fastenedto a rod 59. A balancing spring 60, the presence of which is optional,bears against the piston 58. The chamber 56 extends on the other side ofits zone of connection to the chamber 62, which is at right angles toit, in order to form a ball reception zone 63. The main part of thechamber 62 forms in fact a reservoir for a plurality of balls, which arefive in number in the embodiment illustrated in the drawing, the firstball 64 being green in color and the others 65 being red in color.

In its zone situated beyond the chamber 56 this chamber 62 delimits acompartment 66 enabling only a single ball to be received. The length ofthe rod 59 is such that, depending on the state of the spring 57, itcloses or opens the chamber 62.

At ambient temperature the device is in the state shown in FIG. 24, withthe five balls housed in the chamber 62 and the latter closed by the rod59. When the temperature falls to the set temperature, the spring 57contracts, enabling the piston to move back and open the chamber 62,thus through the action of the relaxing of the spring 67 housed in thelatter enabling the balls to advance, the green ball falling into thecompartment 66 and the first red ball arriving facing the piston 59.

It is to be noted that tongues 68 provided in the crossing zones of thechambers 56 and 62 prevent disordered movements of the balls atundesired temperatures.

In the normal storage position the device is in the position shown inFIG. 25, with the green ball 64 visible through a window 69, thusindicating that the storage temperature has been duly reached. When thetemperature rises above the set temperature, the spring is relaxed andmoves the piston forwards, this movement causing the first red ball 65to pass into the compartment 63, where this ball can be viewed through awindow 70. In the course of each following cycle of fall and rise of thetemperature a red ball is brought into the compartment 63, thus allowingthe user to view directly the number of oversteppings of the temperate.

FIGS. 27 to 30 illustrate a first variant of the device described withreference to FIGS. 24 to 26, wherein the same elements are given thesame references as previously.

This device has an additional original feature because of the presenceof a window 76. Its functioning is identical with the exception that anadditional indication is obtained with the aid of this window 76. Atambient temperature the device is in the state shown in FIG. 27, withthe five balls housed in the chamber 62 and the latter closed by the rod59. Only the spring 57 is visible through the window 76. When the settemperature falls, the spring contracts, enabling the piston to moveback and open the chamber 62, thus through the action of the relaxing ofthe spring 67 housed in the latter enabling the balls to advance, thegreen ball falling into the compartment 66 and the first red bellarriving facing the piston 59.

It is to be noted that tongues 68 provided in the crossing zones of thechambers 56 and 62 prevent disordered movements of the balls atundesired temperatures.

In the normal storage position the device is in the position shown inFIG. 28, the green ball 64 being visible through a window 69 and thesupport of the piston 58 likewise being visible through the window 76.These two indications show that the storage temperature has duly beenreached on the first lowering of the temperature.

When the temperate rises above the set temperature, the spring of analloy which memorizes its shape is relaxed and moves the pistonforwards, this movement causing the first red ball 65 to pass into thecompartment 63, where this ball can be viewed through a window 70.

The support of the piston 58, however, is no longer visible in the newwindow 76, as shown in FIG. 29. Nevertheless, it may be that the rise intemperature is not sufficient to pass the predetermined criticalthreshold, so that the red ball will not be ejected because the memoryspring is not sufficiently relaxed. This possibility will be indicatedby the device, because the support of the piston 58 will no longer bevisible in the window 76.

In the course of each following cycle of fall and rise of temperature ared ball is brought into the compartment 63, thus enabling the user toview directly the number of oversteppings of the temperature.

FIG. 30 shows the first fall in temperature following an inopportunerise in temperature described in connection with FIG. 29. When thestorage temperature has been reached again, the support of the piston 58is again visible in the new window 76. If it is not visible and thedevice is in the configuration shown in FIG. 30 (one red ball ejected),this means that the temperature is higher than the storage temperature.

FIGS. 31 to 34 illustrate a second variant of the device previouslydescribed with reference to FIGS. 24 to 26. Compared with that device ithas an original feature because of the presence of a large window 77disposed in the zone of deflection of the spring 57 of an alloy whichmemorizes its shape, this window being provided with a linear graduation78 (a, b, c, d); the functioning is the same as that of the precedingdevice, with additional indications. At ambient temperature (FIG. 31)only the spring 57 is visible facing the graduated window 77.

When the temperature falls to the set temperature, the device is in theposition shown in FIG. 32, with the green ball 64 visible through awindow 69 and the support of the piston 58 likewise being visiblethrough the window 77, facing one of the graduations 78b.

These linear graduations correspond to a series of temperatures for agiven spring 57 of memory alloy.

Thus, for example, in this case

a=-13° C.

b=-16° C.

c=-19° C.

d=-22° C.

In FIG. 32 the temperature is -16° C. It is thus possible for the exactvalue of the temperate to be continuously known when the device is atstorage temperature.

When the temperature rises above the set temperature, as is illustratedin FIG. 33, a red ball 65 is ejected into the compartment 63, where itis viewed through the window 70. The support of the piston 58, however,is no longer visible in the window 77.

An advantageous variant of this device, illustrated in FIG. 34, consistsin sufficiently enlarging the width of this graduated window 79 todetermine instantaneously what the temperature is between for example:

a=+5° C.

b=0° C.

c=-5° C.

d=-10° C.

e=-15° C.

f=-20° C.

g=-25° C.

FIGS. 35 to 37 show three views in section of another device making itpossible to indicate the durations of the overstepping of the differentpredetermined temperature thresholds.

This device comprises a casing 81 of parallelepipedic general shape, inwhich an elongate chamber 94 is provided. At one end this chambercontains a spring 92 of an alloy which memorizes its shape, of whichspring one end is fastened to the bottom of the chamber while the otherend is supported against the head of a piston 93 fastened to a rod 88. Abalancing spring 87, the presence of which is optional, bears againstsaid piston 93. The chamber 94 has a second part, separated from theother part by a baffle 86. In each part of this chamber 94 is situatedat least one clockwork mechanism 85, 89 coupled to a revolution-countermechanism 84, the triggering of which is effected with the aid ofspecific pushers 83, 91 operating a switch 82, 90.

At ambient temperature the device is in the state illustrated in FIG. 5,with the spring 92 which memorizes its shape relaxed and the piston andits rod 93 occupying the entire left-hand end of the elongate chamber94. The balancing spring 87 is compressed between the baffle 86 and thesupport of the piston 93.

Because of the absence of the support of the piston 93 under the pusher91, the switch 90 is not operated and the clockwork movement 89 for theset (storage) temperature indicates a zero duration and the number ofpassages to this storage temperature is also zero on the revolutioncounter 84_(a).

Despite the presence of the piston rod, the end of which in thegraduated window 95, 96 indicates ambient temperature (for example 20°C.), under the pushers 83 of the clockwork mechanisms for theoverstepping of high temperatures, the clockwork movements 85 indicate azero duration and also the number of passages, which is zero for each ofthe revolution counters 84_(b) and 84_(c).

This is explained by the shape of the pushers 83, which are mountedinversely to the one shown at 91. Thus during the assembly of the deviceat ambient temperature at the factory, although the piston rod is incontact with the pushers, the latter cannot trigger the clockworkmechanisms and the revolution counters.

The device is therefore new and armed and no clockwork mechanism isoperating.

When the temperature falls to the set temperature the memory spring 92contracts, allowing the piston to move back. The support of the piston93 pivots the pusher 91, which triggers the switch 90. The clockworkmechanism for low temperature (for example -18° C.) starts to operate,and the revolution counter 84_(a) does the same, indicating 1.

FIG. 36 indicates this functioning. The end of the piston is situated inthe window 95 at a right-hand end, where the graduation 96 indicates-20° C., or else a lower temperate such as -25° C.

Thus, by looking at the device it is known that:

it has for a period of x hours been at at least -20° C., this is itsfirst passage, and at the moment of time t it is at -25° C. for example.

With regard to the clockwork movements 85 corresponding to theoversteppings of the high temperatures, they still indicate a zeroduration and also the number of passages, which is zero for each of therevolution counters 84_(b), 84_(c). This is due to the absence of thepiston rod under each of the pushers 83, which cannot operate theswitches 82.

In the storage position only the clockwork mechanism for the storagetemperature functions, and its revolution counter indicates 1.

When the temperature rises above the set temperature, as shown in FIG.37, the memory spring 92 relaxes and moves the piston forwards, and,depending on its amplitude, this movement:

stops the storage temperature clockwork mechanism because of the absenceof the piston head under the pusher 91,

triggers at least one of the clockwork mechanisms for high temperaturesbecause of the presence of the piston rod under the pusher 83, whichoperates the switch 82, the time starts to be indicated and therevolution counter marks 1 (84_(b)).

If the amplitude of the movement is greater (the temperature is higher),the piston rod operates the second pusher 83, the second clockworkmechanism starts to operate and the revolution counter 84_(c) marks 1.

The temperature of the device can be continuously read through theposition of the left-hand end of the piston rod facing the graduation 96of the window 95.

When the temperature falls back to the set temperature, the memoryspring contracts and the support of the piston 93 once again pivots thepusher 91, which triggers the switch 90. The clockwork mechanism for lowtemperature starts to run again, and the revolution counter 84_(a)indicates 2.

When there is another rise in temperature, it will be the clockworkmechanism or mechanisms for high temperatures that start to run again,as well as the revolution counter or counters which indicate 2.

The clockwork mechanisms may be mechanical (at all temperatures from-150° C. to +130° C.), or electronic (at temperatures between -30° C and+60° C.).

The correct functioning of a system of this kind can be monitored at anytime, since in fact:

the number of oversteppings for each high-temperature mechanism mustalways be at least one less than for the storage temperature mechanism,for example:

number of revolutions at -18° C.=x

number of revolutions at -5° C.=x-1

the number of oversteppings for high-temperature mechanisms must obeythe following rule:

number of revolutions at -5° C.=x; the number of revolutions at 0° C.(which is farther to the left in the device shown in FIG. 37) is thenlower than or equal to x. The mechanism must in fact always trigger at-5° C. before triggering at 0° C., if it goes as far as thattemperature. In addition, the duration of the overstepping at 0° C. willalways be shorter than or equal to the duration of the overstepping of-5° C.

Thus, by looking at the clockwork mechanisms and the associatedrevolution counters it is possible to check, through these conditions,whether there is a fault in the marking system (pusher damaged. . . . ).

Instead of a clockwork mechanism for storage temperatures and hightemperatures, it is possible to make use of an electronic systemrecording, when the pusher is operated, all the data and oversteppingdates. The last-mentioned device is the most sophisticated.

Finally, it is possible to have a system of the kind described in FIG.35, which by the addition of an electronic calendar indicates the dateswhen high temperatures are overstepped.

A variant of this system may consist of two windows 95 which havegraduations 96 and are smaller in size, situated at each end of thechamber 94, facing the clockwork mechanisms.

By using a piston 93 whose support is green in color and whose rod isred in color, it would be known at any moment by looking at the windowat the right-hand end:

if the color is greens: all is well and the clockwork mechanism isconsulted, and by looking at the window at the left-hand end:

if the color is red: warning: the temperature has been overstepped andthe clockwork mechanism should be consulted to ascertain the durationsof the oversteppings of the temperature.

FIG. 38 illustrates a rotary actuator which makes it possible to obtainat the same time a longitudinal displacement of the spring type and arotary movement without having recourse to a complex rotary device. Thisactuator has a structure in the general form of a sphere delimited byelements 97 of an alloy which memorizes its shape and made from wires,strips or flat springs. At its end 98 the sphere is fastened to theframe, while its other end 99 is free. A central spring 100 isassociated with the sphere and has sufficient strength to flatten thelatter in the martensitic phase, but too weak to retain it in theaustenitic phase.

When cooled, the elements tend to retract by twisting, so that the fixedand movable ends are brought closer together, with a rotary movement ofthe movable end, which may be as great as 360°. When the temperaturerises, the elements resume their previous position, bringing about anaxial and rotational displacement in the opposite direction. This deviceis adapted to operate a warning system or to drive rotationally a systemcomposed solely of free wheels, without using a rack and pinion pair.

The central spring 100 is not obligatory if the elements of an alloywhich memorizes its shape are educated in two directions, for high andlow temperature. The information transmission means may be similar tothose described for the preceding embodiments. The use of a plurality ofelements of an alloy which memorizes its shape makes it possible toobtain a very high-performance system.

In all the embodiments described above it is possible to use shapememorizing elements which operate with or without hysteresis.

In all the embodiments described above it is possible for one or moresprings permitting modification of the reaction temperatures of thedevice to be associated with the element or elements of a memory alloy.

As is clear from the foregoing, the invention provides a greatimprovement of the existing technique by supplying a device formonitoring the temperature of a product or an article and detecting theoverstepping of the temperature, with immediate visual indication of anoverstepping and counting of the number of oversteppings.

As is obvious, the invention is not limited solely to the embodiments ofthis device which are described above as examples; on the contrary, itincludes all constructional variants.

Thus, in particular, the means enabling thermal inertia to be introducedinto the functioning of the spring could be different, and could forexample consist of a cylinder inside which the spring would beinstalled, without thereby departing from the scope of the invention.

I claim:
 1. A temperature monitoring device, comprising:an elongatedcasing formed with at least one window; a row of cogs formed in saidcasing and shaped to enable unidirectional travel therealong; a cursorin said casing shaped to be retained by said cogs and adapted to bestepped therealong in a direction of uni-directional travel; a springcomposed at least in part of a shape-memory alloy and formed with oneend bearing against said casing and with an opposite end, said springbeing initially deformed upon exposure to a predetermined temperaturelevel; and a rod fastened at said opposite end and longitudinallyshiftable in said casing upon deforming said spring and formed withother cogs engageable with said cursor for stepping said cursor alongsaid rod and said row upon exposure of said spring to anothertemperature, whereby a position of said cursor along said row can beviewed through said window, said cogs on said rod being spaced by adistance corresponding substantially to a stroke of said spring betweensaid predetermined temperature and said other temperature.
 2. Thetemperature monitoring device defined in claim 1 wherein said rod isformed at an end connected with said spring with a piston, said pistonbeing connected with said spring, said rod being formed with a shoulderand carrying a ring adjacent said shoulder whereby said shoulderdisplaces said ring in a direction toward said spring upon an initialretraction of said spring to bring said ring into view through a windowof said casing.
 3. The temperature monitoring device defined in claim 1wherein said cogs are shaped with surfaces inclined to said directionand surfaces perpendicular to said direction, said spring being bracedbetween and secured to two cursors engageable by said cogs whereby saidcursors are stepped along said row upon alternating contraction andexpansion of said spring.
 4. The temperature monitoring device definedin claim 1, further comprising means on said casing delaying deformationof said shape-memory alloy in response to a variation of temperature. 5.The temperature monitoring device defined in claim 4 wherein said meansdelaying deformation includes a ring on the casing.
 6. The temperaturemonitoring device defined in claim 1 wherein said casing has a wall of athickness delaying deformation of said shape-memory alloy in response toa variation of temperature.
 7. A temperature monitoring device,comprising:an elongated casing formed with at least one window; a row ofcogs formed in said casing and shaped to enable unidirectional traveltherealong; a first cursor in said casing shaped to be retained by saidcogs and adapted to be stepped therealong in a direction ofunidirectional travel; a second cursor spaced from said first cursoralong said direction and engageable by said cogs, said cogs being shapedwith surfaces inclined to said direction and surfaces perpendicular tosaid direction; a spring composed at least in part of a shape-memoryalloy and braced between and secured to said first and second cursors,said spring being initially deformed upon exposure thereof to apredetermined temperature level and effective, upon exposure to anothertemperature, to step said cursors along said row upon alternatingcontraction and expansion of said spring, whereby a position of saidfirst cursor along said row can be viewed through said window.
 8. Thetemperature monitoring device defined in claim 7 wherein saidshape-memory alloy possesses hysteresis, a rearwardly one of saidcursors with respect to said direction having a rod extending movablythrough a forwardly one of said cursors, said rod having an endprojecting beyond said forwardly cursor and formed with a shoulder, acompensation spring being braced between said shoulder and saidforwardly cursor.
 9. The temperature monitoring device defined in claim7 wherein one of said cursors is composed of a shape-memory alloy. 10.The temperature monitoring device defined in claim 7 wherein arearwardly one of said cursors with respect to said direction has a rodextending movably through a forwardly one of said cursors, said rodhaving an end projecting beyond said forwardly cursor and formed with ashoulder.